A model of the combustion of a porous carbon particle in oxygen is developed. The model considers heat and mass transfer in both the gas phase above the particle's surface and inside the porous particle. The conditions for the model having a solution have been determined by solving the diffusion equation in the gas phase around the particle. Two regimes of particle combustion have been analyzed: 1) the regime when carbon reacts with oxygen in the all volume of the particle, and 2) the regime with carbon reacting with oxygen in a layer at the particle's exterior. Both carbon monoxide and carbon dioxide can be formed in the first regime, but carbon monoxide can only be formed in the second regime. ne conditions for each regime of particle combustion are determined.